The present invention relates to a double core barrel for carrying out boring and core drilling operations, e.g. in oilfields, and to a method of adjusting the spacing between a boring bit and an extractor cone in the core barrel.
The double core barrel basically comprises a rotating external tube and a fixed internal tube. The lower end of the external tube is provided with a boring bit. The lower end of the internal tube is provided with an extractor cone. The upper end of the inner tube is screwed onto the lower, non-rotary portion of pivoting means enabling mechanical connection between the inner tube and the outer tube. The upper rotary portion of the pivoting means is screwed into a screw-threaded body which is part of the outer tube. The upper portion of the pivoting means therefore rotates in conjunction with the outer tube.